Tooth loss has lead to shortened life span, compromised quality of life via socially unacceptable appearance and the simple inability to masticate food as the first part of digestion. For the last several decades dental implants and dental prostheses (crowns) placed upon the implant system have become predictably successful and accepted from the aspects of medical biology, dental esthetics and masticating function.
Once the dental implant is placed and secure in the bone-receiving site a second structure has to be placed upon the dental implant body called the abutment. The abutment is held to the implant body by a screw. Screw loosening due to biting (occlusal) forces as well as frequent temperature changes of over 100 degrees F. from hot versus cold foods and liquids cause screw loosening to occur. Imperfections in the manufacture of dental implant systems also contribute to screw loosening. This has been reported to be as high as 65% over a three year period of time in past literature. (IMPLANT SCREW MECHANICS, Edwin A McGlumphy, DDS, Ms, Deborah A Mendel, DDS, and Julie A Holoway, DDS, Dental Clinics of North America Volume 42. Number 1. January 1998)
Screw loosening of the dental prosthesis can cause damage to the approximating and opposing dentition such as tooth loosening and fracturing. Loose screws themselves are much more likely to fracture and, if unable to retrieve the now fractured screw end, it may necessitate surgery to remove the useless dental implant body, and, if possible, surgically place a new implant body. Loose screws are cited as the cause of the submersion of dental implant bridges where at least one tooth abutment is a natural tooth and one or more abutments is a dental implant. The submersion of a natural tooth in this circumstance can necessitate extensive dental treatment to correct the damaged tooth and bridge. In addition, re-tightening a loosened screw requires, at a minimum, a visit to a dental practitioner and some means of gaining access to the implant abutment screw head. If the screw head is accessible through the prosthetic crown via an access filling (not shown) the screw can be tightened and a new replacement access filling placed as a consequence of a dental office visit. If, however, the abutment screw is not accessible via an access filling on top of the crown prosthesis (which has become more and more the common practice) the crown prosthesis then needs to be removed from the abutment which may necessitate damage or destruction of the prosthesis requiring as much as several patient visits to the dental practitioner to take impressions, make a temporary crown and replace the re-fabricated new crown prosthesis. In either case, the loosened screw is an expense to the patient in terms of time and money and an expense to the dental practitioner in terms of his or her time and the professional expense of not living up to a patient's expectations.